Contact plug



Jan. 28, 1.941. A. BRowNsTElN y 2,229,794

CONTACT PLUG Filed March 5, 1937 INVENTO R Bihar Brow/sian v ATTORNEY Patented Jan. 28', 19211 UNITED STATES PATENT OFFICE CONTACT PLUG Arthur Brownstein, Bridgeport, Conn., assgnor to Electrix Corporation, Pawtucket, R. I., a corporation of Rhode Island v Application' March 5, 1937, Serial No. 129,235

- 3 Claims.

This invention relates to a new and useful contact plug and more particularly to a resilient contact' plug. A contact plug so-called generally refers to the bladed fixture at the end of a vg5 wire conductor which makes the necessary electrical contact when pushed into the complementary recesses inan electricaloutlet or other suitable socket, all as hereinbelow described.

Resilient contact plugs or rubber contact plugs as they are commonly called because rubber is the insulating material usually used in their manufacture, are favorably received in the electrical trade. 'Unlike `molded resins, hard rubber or similar contact plugs they are-not subject to l5 easy fracture and inasmuch as they are pliable the contact or connector blades can adjust themselves to small variations in the gauge or distance between socket recesses. Further, connector blades are more easily and quickly assembled in resilient plugs, generally a simple punch opera- -tion will suiiice and then, too, there is no need of rivets,`screwsor other holding devices. With the harder contact plugs, blades frequently work loose, impair the electrical efficiency o-f the plug 25, and prove a nuisance in general; with resilient contact plugs, the connector blades, on the other hand, are more cheaply, easily and lastingly re tained. Another desirable point is that the electrical jointsbetween the blades and wire conductor ends in a resilient plug are more adequately guarded from strain and insulated in and by the plug itself. Yet, resilient contact plugs can be molded with ease and at low cost.

Prior to this invention and at present, resilient j contact plugs have been and are made and sold in which the connector blades are retained by distortion of the rubber. There are certain drawbacks in this type of resilient plug. In the first place, the connector blades are not too securely held because the-very portion of each blade relied upon to produce the desired distortion for purposes of holding the blade in place in the plug at the same time prevents maximum surface contact between the surface of the blade 4,5V and the adjacent surfaces ofthe plug. To remedy the wobble induced thereby, recourse frequently is had to a Wedging piece tobe tightly fitted into thevplug between the blades. This wedging piece has a steadying effect on the blades rela- 50 tive to the plug and resists their being pulled out with undue ease. A second type of resilient plug has the blades. and wire conductor on the underside ofa substantial rubber block over which -ts a rubber cap threaded onthe wire conductor Y 55 to cover the Whole assembly save for the side of the block through which the blades protrude. This two piece plug is liable to having its parts separate, is very expensive and lacks the more secure holding of the blades which is an object of this invention.

It is the object of this invention to produce a resilient contact plug in which the connector blades are held in a positive manner against movement in either direction along their longitudinal axes. Itis also arr object of this inven- 10 tion to produce a contact plug of this type having but one part i. e., a one-piece plug.

It'is also an object of my invention Ato produce a resilient contact plug in which there is maximum surface contact between the connector 15 blades and the plug bodyand at the same time the blades are prevented byvpositive` means from being pulled out of or pushed down into the body of the plug.

It is also a primary object of this invention to 20 achieve a new and important method of assembling connecto-r blades and resilient contact plug bodies.- A further object is a resilient contact plug in which the connector blades and wire conductor ends are assembled from the small 25 end of the plug.

A further object is the production of a resilient contact plug in which there are positive restraining means for the conductor blades and yet which is successfully moldable. Particularly 30 is this an object in connection with the onepiece contact plug which is an object of this invention.

In a preferred embodiment of this invention there is a one-piece molded body of such a con- ,35 struction that in the assembly thereof the blades and conductor wires therefor are inserted through the small end of the contact plug into proper slots therefor provided until the blades reach and are held byl positive means in their 40 permanent position. The body of this plug is molded so that while the mold dies are being withdrawn there is no undue'tearing or straining I of any part of the body of the. plug. 4This preferred form of contact plug has two blade slots of rectangular cross-section which extend in to the interior of the plug and there join to' form a common channel opening out at the small end thereof. This channel forks at the point where it divides .and its parts join the lower ends of the respective blade slots. Blade slots are commonly made of slightly smaller dimension than the blade in cross-section so as frictionally to grip and hold the blade when it is assembled in place. 55

Near the lower end of each blade slot .are to be found small integral blocirsof equal sige on opposite sides of the slot. 'I'hese blocks thus constrict the passage through the slot exceptl for a relatively smaller passage therebetween. Placed in this fashion the blocks are adapted to engage in complementary recesses inthe blades when they are assembled therewith. 'I'hus the blades should preferably be recessed to engage with the blocks previously described and the ends thereof maybe beveled or curved so that when the blades and plug body are assembled together the passage of each blade through the constricted portion betweenthe blocks is effected easily because the blocks separate suiiiciently when pushed back because of the resilient material in the plug.

`When the blocks are opposite to the blade recesses they snap into positive engagement fixing the blade in place andl effecting one of the objects of this invention. i..

In assembling the preferred embodiment of the contact plug of this invention, it must be done, of course, as will appear in more detail below,

through .the small end thereof. At the point4 where thevchannel therein forks, the dividing wall serves as a guide for the blades being pressed towards their respective slots.

Although the preferred embodiment just 'described has lcertain physical characteristics, it is entirely possible at the same time to stay within the-` spirit of this invention and yet depart from the precise form thereof by the exercise of mechanical For example, the blocks located in the blade slots may be one in number ormore,

may be set opposite to one another or may be staggered along the length of the slot. Likewisefor example, each blade slot may be extended further into the contact plug and the blocks located at any point along its length. Further, the guide wall of the channel at the lower end of the blade slots might be completely removed or on the other hand it might be increased insize even to the point where there will be two separated combination blade slots and channels ex tending through the plug from one end towthe Another change that can be made is to remove excess material from the plug parallelv to nthe plane of the two blades and thus produce a flatter plug. Thereis even a possibility( that the blades can carry the blocks and the slots have the recesses. In such acase, a specialmold die wouldv have to be Omade.

Other objects, advantages and features of this invention willl appear from the drawing and the followingdescription.r

In the drawing: l

Fig. 1 isa perspective view of a contact plug embodying this invention'ln full assembled relation with the wire conductors therefor;

Fig. 2 is a top view of the contact plug of Figurel; s

Fig. 3 is a cross-sectional View taken 0n linie 3-3 of Figure 2;

Flg. 4 is a cross-sectional view taken on line 4 4 of Fig. 3;

Fig.5 is a cross-sectional view throughv the `center of the body of the contact plug shown in of this invention; f

Fig. 7-ls a cross-sectionalview through-the center of the body of the contact plug shown .inFigure 6;

Fig. 8 is a view in perspective elevation of connector blades ready for insertion into the body of the contact plug' of .this invention; and

' Fig. 9 is a cross-sectional view in elevation of the contact plug assembly,

Referring to the drawing, I0'is the body of the form of a resilient contact plug covered by this' invention shown in Figures 1 through 5. 'I'his plug has two ends which shall be designated the small end II and the large end I2. Protruding from the faceof thel large fend are two contact or connector blades I3 and I4. 'I'he usage of this type of contact plug is familiar to everyone. v

Returning to the drawing, body- I Il is a onepiece resilient member so recessed as to be capable of holding blades I3 and I'4 most securely and nyet it is readily and successfully moldable. If

Figures 3 and 5 are inspected it will be seen that with the use of a multiple part mold (see Fig. 5'A), the removal thereof can be had without hindrance. Of the various recesses in body I0, the blade slots for blades I3 and I4 are numbered I5 and I8 respectively. These slots naturally are tight-fitting around the lower ends of the blades 'which they hold. At the lower ends of the blade slots I5 and IB are' to be found the blocks which constrict or obstruct the otherwise free passage, except for reasonable friction, of the respective blades through the slots. For blade slot I5 the Gblocks are numbered I1 and I3 and for slot I6 the blocks are I3 and 2liv (see Fig-4). blocks are integral with body III and are adapted to cooperate with recesses in blades I3 andv Il. If blade I3 is taken as an example (Fig. 3) it will be seen that recesses 2I and 22 exactly iit over blocks I'I and I8 respectively wherebyblade I3 when in final position` is keyed or locked in place and prevented from either being pushed further `down into or from being pulled out ofslot I5.

. to help keep any pulling pressure` on its wire conductor 24 awayi'rom the soldered electrical joint 25 between the wire end 24 and blade I3 this by means of a U-turn through-recess 23 (see Fig) Indeed, so snug is the f it between blade slot .I5 and blade I3 that the Vend of wire conductor 2d if turned over'the top of the central. integralwall 2b and down into slot I5 (see Fig. 1) will be firmly held when blade I3 is pushed down therein even if no soldered Joint'25 is made.

These In assembling the contact plug as'shown in Figure 1, the blades have been inserted into bldy Y III from the large end. This is made possible yplunger sections are because the lower ends of the blades do not exceed the upper ends in width, which is uniform where the blades are not recessed. In such an assembly the wire conductors 24 and 21 pass through a circular opening in the center of the plug, are attached to their respective blades I3 and |4 and then with the blades are pressed or pushed down into the respective blade slots. In

such assembling, for example, the lower curved end of blade I3 would part the blocks |1 and I6, which yield because of the resilience of body l0 until such blocks come opposite to the recesses 2| and 22 when the spring in the resilient body I0 returns the blocks to their original positions, locking blade I3 in place without any distortion or severe strain being thereby imposed upon the resilient material of body I0. Onthe face of large end I2, a depression 28 is to be found which permits the wire conductors 24 and 21 to bend over the discontinuous wall 26 without sticking up above the face of the plug.

If Figure 5 is next observed it will be seen that the blade slots I5 and I6 extend downwardly beyond the bottom of wall 26 and into a common channel 29. In the plug of this design the blades with the wire conductors attached may be pressed instead into their iinal assembled position (see Figure 1) through the small end of the plug. In such a case the blades will be pressed upwardly through the constricting or 'obstructing blocks, the bevel 30 on the upper ends of the blades assisting in such passage. In such a case, likewise, the wire conductors would not pass through the circular opening 3| in the center and `yet the wire conductor cable 32 would be far enough inside of small end Il to comply with electrical safety regulations.

In molding the plug body shown in Fig. 5, a plural-part mold as shown in Fig. 5A can be used. This mold has the advantage among others of being able to mold the blocks I1, I8, |9 and 20 in the respective blade slots of body I0 and of being removable thereafter without distortion or breakage of any part of the freshly molded body. The mold in question comprises a jacket portion |0a conforming interiorly to the outline of body III and two plunger sections. Referring to the drawing, it will be seen that in the plunger sections there is a portion 23a forming the common channel 29, a table portion 28a for the depression 28, spindle portions 66 and 61 needed to form opening 3| and members 65 and 66 to form the blade slots. Reduced portions |8a and 20a of members 65 are responsible for forming the blocks. In molding, a proper sized ball of soft rubber is placed in jacket portion Ilia and the then thrust into the jacket portion, sealing it and interacting to form the plug body Ill. When the plunger sections kare withdrawn, there is no catching of any part of the mold or plungers on any part of the plug body and consequently there is no distortion, tearing or breaking of the latter. The principal factor in achieving this result is due t0 the division of the-mold portions forming the blade slots across the reduced portions responsible for forming the blocks. With a few changes which are now readily apparent a successful mold embodying the sameprinciples can also be made for the vembodiment, of this invention shown in Figures to 9.

The embodiment of the invention shown in Figures 6 through 9, is apreferred form. In this contact plug, body 46 has a small end 4| and a' large end 42. -The face of end 42 is pierced solely by the blade slots 43 and 44. There is usually more material at this end than at the small end 4| because any tendency to separation or pinching the blades vtogether is resistedprimarily and largely perforce by the large end. At the lower 'end of slot 43 are to be found integral blocks 45 and 46 (for slot 44 but one block 41- Figure 7-is shown). These blocks have the same functions, purposes and actionras those described in connection with the embodiment shown in Figure 1. At about the point where the blocks are located, the blade slots open into the upper forked sections of a common channel 48. The ,forked sections are caused by an integral partition or wall 49 which when the plug is being assembled serves to guide the end of each blade into its respective slot. Ample room is provided in the channel 48 and the forked sections thereof to 'accommodate the Wire conductor ends 50 and cable 50a (see Figure 9). It is also'entirely possible to design this plug so as to decrease the length of channel 48 and its sections by lowering wall 49 or some similar change. This would more completely place the blocks actually in the blade slots and would decrease the room in the channel and sections `for the wire conductors.

In Figure 9 is blade 5| in assembled position with its recesses. 52 and 53 engaging blocks 45 and 46 respectively. The strain recess 54 with the bent over wire end 50 is also shown. As explained previously the snug t of slot 43 around blade 5| produces maximum surface contact and the steadiness required without having to make a two-piece contact plug. In fact, this preferred form of contact plug provides the most complete, distortionless\and satisfactory Ahold for its blades. Added to this, the entire body 40 is made in one piece. Like the other form shown in this application it can readily be molded with the blocks therein as shown. y

In assembling the preferred embodiment, blades arranged substantially as in Figure 7, are pushed into their respective blade slots 43 and 44 until the blade recesses and blocks engage (Fig. 9) small end 4I and the passage of each blade past its obstructing blocks is as previously described for the other embodiment of this invention shown in this application. When assembled, all electrical parts which should be covered are completely protected and insulated and the blades are firmly and immovably held in place without the aid of anything except the contact plug itself.

This invention is not to be limited in any way except as may bedone by the appended claims.

I claim:

1. In a contact plug, a one-piece base of resilient exible material having a central recess adapted to receive a cord and two fiat slots extending downwardly therefrom through the plug, said base having integral spaced separate parallel portions in each slot projecting towards each other to form restricted slot passageway portions extending from within each slot into the central recess, said projecting portions having shoulders f at each end thereof.

2. In a contact plug, a one-piece base of resilient flexible material having a central recess adapted to receive a cord and two 'at slots ex-y tending downwardly therefrom through the plug,

. said base having integral spaced separate parallel portions in each slot projecting towards c ach other to form restricted slot passageway portions extending from within each slot into the central Allof s uch assembling is done through recess, said projecting' portions having shoulders at each end thereof, and straightI contact blades seated in saidslots, said blades having recessed portions adjacent the upper ends thereof engaging the parallel portions of said slots.

3. In a contact plug, a one-piece base of resilient flexible material having a centraLrecess adapted to receive a cord and two flat slots extending downwardly therefrom through the plug, said base having integral spaced separate parallel portions in each` slot projecting towards each other to form restricted slot passageway portions extending from within-each slot into the central recess, said projecting portions having, shoulders at each end thereof, and straight contact blades seated in said slots, said blades having recessed portions adjacent the upper ends thereof engaging the parallel portions ofsaid slots, the intermediate portions of said blades below said recessed portions having transverse slots for connecting the cord lead wires. Y

ARTHUR BROWNSTEIN. 

